1. Field of the Invention
The present invention is related to oil drilling equipment, and more particularly, to an apparatus to restrain service loops which transfer electrical, hydraulic and compressed-air power to the oil derrick top drive.
2. Description of the Prior Art
Referring to FIG. 1, a top drive drilling system which has a notation number of 3 in FIG. 1, is a common piece of machinery in an oil well drilling tower 1 in the oil drilling industry. The top drive 3 includes an AC or DC motor or a hydraulic motor which is connected to a speed reducing (torque increasing) gearbox, so that it can rotate the drill pipe to bore an oil well. The top drive is mounted in the drilling derrick and travels up and down under a control of a piece of traveling equipment 2.
Referring again to FIG. 1, there is illustrated an umbilical system 6 which is commonly called service loops. The service loops 6 are part of hoses 5 of the machinery in the oil well drilling tower, where each of the hoses transfers the respective electrical; hydraulic and compressed-air power to the top drive. There are various combinations of hoses, wires and cables that pass through the inside diameters of the service loops. Most top drive utilize a combination of two to four service loops which have approximately equal length. Each service loop at one end is attached to the derrick (or mast), and at the opposite end is connected to the top drive. As the top drive travels up and down, the service loops move accordingly up and down in the longitudinal direction. In addition, they have a bending movement in the transverse direction, which forms the respective bend radii.
The service loops 6 of the hoses vary from about 2 inches to 7 inches in diameter. In addition, there are also variations of the hose structure and materials according to their usages in the drilling process. For example, a hydraulic pressure could be up to 3000 psi, and therefore, a hose to transfer the hydraulic fluid must be mechanically enhanced by having a sufficient thickness and an appropriate material structure. In general, the service loops have a composite structure to achieve reinforced mechanical properties. The composite-structure is comprised of an inner liner, a middle braid and an outer liner. The inner and outer liners are made of thermoplastic materials or rubber. The middle braid is the composite of the thermoplastics and enhanced polymeric threads or metal wires. Therefore, the mechanically enhanced hoses have large longitudinal rigidities.
It will be appreciated that due to the variations of the hose diameters, material and structure which all affect the longitudinal flexibility of the hoses, each service loop does not always have the same bend radius. The hoses having a smaller diameter usually have a smaller bend radius, and the hoses having a larger diameter have a larger bend radius. For example, in general, hoses with two inches in diameter will have 30 inches in bend radius, hoses having three inches in diameter will have a bend radius of 42 inches, and hoses having four and half inches in diameter will have a bend radius of 48 inches. Therefore, the bottoms of the service loops travel in different paths when all the Loops having the same length travel in the longitudinal direction.
The variation in paths during operation of the machinery causes the loops to become entangled. When this happens, loops with the larger diameter have the tendency to force loops with the smaller diameter into unnatural positions, which results in premature failure of the loops with the smaller diameter. In this situation, an environmental condition such as a strong wind also plays a factor to accelerate the failure of the loops. In addition, in some cases two or more loops with the smaller diameter can displace a loop with the larger diameter, which can cause problems including broken loops.
If the loop failure happens, it will not only cause a loss in economic value due to costs to replace the damaged loops and down time for replacing the loops, but also create a hazardous situation such as leakage of the high pressured air or fluids to machine operators. Therefore, finding a solution to this problem becomes an industry priority.
Over the years there have been several attempts to design metal clamps to wrap around the loops so that proper spacing and consistent travel paths could be maintained. However, these attempts have failed due to the continual forces on the rigid clamps and the harsh environment the clamps are subjected to.
Therefore, there is a significant need to provide an apparatus for flexibly restraining the service loops to significantly improve safety conditions and increase productivity in operation of oil drilling wells.